Let's hang on here Nikolailev, doing all of those nerfs at the same time is a bad idea. I don't know if you've had the "Pleasure" of playing EA or SOE games but one of their biggest issues is TERRIBLE balance, because the buff underpowered things by a ridiculous amount then nerf overpowered things by a ridiculous amount. Basically what was OP last week becomes a completely useless and pointless build. (examples available upon request) Now reducing the arc OR slowing down it's rotation OR reducing its AOE are all good idea's but implement them one at a time and give it a week to see if it is a good balance. I mean all they did to make it suddenly viable was boost it's projectile speed, add some zoom, and make it have a slightly bigger arc.
I guess my point is this, they made 3 changes to make the artemis viable lets not do 3 changes and send it back into obscurity. Honestly as it is now it's still a debate for me to take the Artemis to keep myself safe or a flak cannon to get kills. It really depends on the reliability of my other captains and my current crew.
Your principle is completely sound. However, it's just a matter of tweaking the nerfs so that it isn't too drastic. Reducing the firing arc by 20 degrees (major) and reducing the AoE by 1 (to 4, minor) wouldn't throw it off by much. And remember, it still retains its huge damage output, range, and accuracy. It wouldn't be a huge nerf.
It's also not a nerf to the weapon's primary role. It should be a good disabling weapon at range. These nerfs are geared at nerfing the secondary role it shouldn't have; close-in disabling. The awesome firing arc, turn speed and AoE make it good at that, and
that's why it's overpowered. The Artemis should be weak at close range, but excellent afar.
I'm really not sure why it was an obscure weapon a few patches ago, because it was still awesome. I suspect it was a case of the metagame, because no one knew how good it was. I know I made use of it to good effect back then (even before the buffs it likely didn't need). Now that people are beginning to realize how great shatter is (again) it's becoming more and more common.